Download CYTOKINE AND LYMPHOCYTE SUBSETS SMALL GROUPS

Host Defense 2012
Small Group Problem Solving Sessions
Cytokines/T-Cell Subsets
Cytokine Small group Master Answers
Master Answer to Case 1
Orchestrators of the Immune Response

Leprosy can incite either a Th1 (helper) or Th2 subset dominant response. The
dominant subset is influenced by route and dose of antigens (M. Leprae), status of
the patient, especially nutritional (malnutrition is associated with depressed Th
function), and MHC/TLR dictation of the immune response. HIV infection or
other diseases (cancer for example) that could affect the patients’ immune system
could also play a role. The expression of the tuberculoid form of leprosy can be
further influenced by any drug that inhibits T cell or macrophage activation. Thus
cyclosporine (an immunosuppressant drug) or corticosteroids (potent antiinflammatory drug) can convert tuberculoid leprosy to the more lethal form.

Conversely, if the activated macrophage in a granulomatous (Th-1) lesion in a
patient with tuberculoid leprosy is threatening vital structures (for example: here
the brachial plexus) it may be therapeutically advantageous to suppress the
dominant Th1 subset while treating the actual infection with antibiotics to
attenuate the granulomas and prevent irreversible destruction. Corticosteroids that
suppress IL-1, IL-6 and TNF-; and anti-TNF monoclonal antibodies, have been
used clinically to suppress destructive TH-1 responses.

The genes that would be considered in a vaccine would be Th1, including IL-12,
IL-12R; IFN- and IFN-R; IL-21 and IL21R and/or any other in the Th1
sequence that you think are critical to an effective response. Genes that produce
Th1 TLR activation via DC or Toll like receptors could also be possibilities.
 Master Answer for Case 2

Orchestrators of the Immune Response

Here the pathogenic mediator is a soluble protein elaborated in extracellular fluid
by proliferating bacteria. The response needs to be rapid and one mediated by
antibodies that neutralize the toxin.

In order to develop a vaccine, the antigen needs to be a toxoid type of protein that
mimics the real toxin and stimulates Th2 responses that will promote antibody
formation. IL-4 (could be combined with IL-6 and 10, and/or 21) would be the
most logical cytokine needed as an effective vaccine promoter and one that could
be linked either to a toxoid type derivative of the toxin or to inserted into a
microbe that has been engineered to produce a toxoid antigen.
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Host Defense 2012
Small Group Problem Solving Sessions
Cytokines/T-Cell Subsets

Using the concept of passive immunity, an effective and life saving treatment
strategy in patients with heart involvement would be the use of intravenous antitoxin IgG to block the effects of the neurotoxin that has not irreversibly bound to
the conducting system. The source of this blocking antibody could be from
recombinant synthesis, removal from a survivor of the disease or a previously
vaccinated patient.
 Master Answer to Case 3

Orchestrators of the Immune Response

The setting of this unusual outbreak of disseminated lethal infection by a usually
quite benign attenuated tuberculosis vaccine suggests that there was clustering of
a genetic defect causing a unique immunodeficiency state characterized by
susceptibility to mycobacterial illness.

There is a high degree of intermarriage in many of these villages and genes with
lethal consequences can emerge. In this particular instance, the genetic defect
being passed through the interbred families could either, but not limited to, be a
defect in Th-1 cytokine production, defective Th-1 cytokine receptor synthesis or
loss of function mutations of Th1 activating TLR. The most likely defect is either
in IL-12, IL-18 or INF-γ. There have already been families (and recently a patient
at Loyola) documented with interferon receptor defects that are highly susceptible
to tuberculous type infections.

For the purposes of our discussion, IL-12R receptor deficiency could be just as
likely and this experimental deficiency in mice is also characterized by high
susceptibility to mycobacterial infections. The simplest way to begin tracking the
possible genetic defect would be to extensive haplotyping of the affected children,
their parents and the unaffected siblings. In this case, the recessive defect was
found on chromosome 6.

The in vitro testing that would document the deficiency employs assays of the
mononuclear cells of the affected siblings parents and normal sibs. One possibility
would be to probe mononuclear leucocytes isolated from these subjects with
antibodies to the receptors that could be involved. Since it appears that the
ultimate lethal defect in these patients is their inability to upregulate TNF-
because of a deficiency in interferon-, assays can be devised to measure whether
their mononuclear cells could indeed do so.

It is very important that you understand the principle underlying the use of
tuberculosis skin testing. The test exploits the fact that a TMMI response is
necessary to resist tuberculous infection. If an individual currently has or had
exposure to TB in the past and successfully eradicated it or forced it to lie
dormant in hilar lymph nodes, that individual should have immunologic memory
of the encounter. The immune system can be ‘tricked” into thinking it is
Rev 11/26/11
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Host Defense 2012
Small Group Problem Solving Sessions
Cytokines/T-Cell Subsets
encountering the TB organism again by placing KILLED TB antigens under the
skin. Memory Th cells will generate a TMMI response at the site of the deposited
antigen and this can be detected by the formation of a nodule caused by the
recruitment of macrophages by IFN- producing Th cells. If an individual has
been previously infected but has a genetic defect that prevents TMMI, OR is on a
drug that suppresses TMMI, the skin test will be negative.

The killed skin test antigen is a very poor immunogen and a single test will not
induce immunity, however the BCG vaccine is a live organism and acts as very
weak immunogen inducing some resistance to TB. Problems with the skin test
will become moot soon. A new test, Quantiferon Gold, is rapidly replacing the
skin test. It is much more specific and sensitive and less labor intensive and does
not require subjective human reading of a bump on the arm. The basic
components of the assay are: patient mononuclear cells from the peripheral blood
are incubated with very specific TB antigens. If the patient has immunity to TB,
IFN- will be released and can be detected, even if present in minute amounts.
 Master Answer to Case 4

Orchestrators of the Immune Response

The polymorphism of MHC in the outbred human population makes it highly
likely that there will be a wide range in the intensity of an immune response to a
given antigen and it follows that there will be a parallel diverse spectrum of
disease expression ranging from no clinical symptoms at all to death.

The variance in reactivity to antigens is due, in large part, to differences in how
they are presented by the varying MHC Class I and II determinants to immune
effector cells and /or the type of TLR that is activated on DC. The ensuing
response can range from literally none at all to potent cytotoxicity and granuloma
formation to exuberant antibody formation with all possible combinations in
between.

In the cases presented, one unfortunate model plane enthusiast either was exposed
to a markedly greater amount of fungus and/or couldn’t generate an effective
killing response to the fungus because of the way his DC presented the antigen to
T cells-the end result is fulminant respiratory failure. The remainder of the group
had the capability to generate adequate antifungal responses and maintain normal
respiratory function. Their symptoms remained those of cytokine activation onlyfatigue etc.

In the drug abuser group, at least 2 individuals could not generate any effective
cytotoxicity to the virus-presumably based on polymorphic TLR and DC- and
died from liver necrosis secondary to viral destruction while 6 had normal
immune responses to a viral infection.
Rev 11/26/11
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Host Defense 2012
Small Group Problem Solving Sessions
Cytokines/T-Cell Subsets

The twin offered a rare opportunity to be the source of histo-compatible CD8
cytotoxic cells directed against the virus that is killing his brother. CD8 cells
could be removed from the twin and expanded ex vivo by exposure to hepatitis
virus antigens and then re-infused into the dying twin. Remember this strategy
could backfire if there is a vigorous response to the virus because the liver could
suffer collateral damage!
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